Multiple photocells



May 29, 1962 Original Filed July 23, 1958 F. F. STROTHER MULTIPLEPHOTOCELLS 2 Sheets-Sheet 2 /2 1N VENTOR /Tkfp p Srno rf/ER BM Vga/1%#Mw) ATTORNEYS United States Patent O" 3,037,122 MULTIPLE PHOTOCELLS FredP. Strother, Shawmut, Ala., assiguor t West Point Manufacturing Company,West Point, Ga., a corporation of Georgia Original application July 23,1958, Ser. No. 750,496, now Patent No. 2,960,417, dated Nov. 15, 1960.Divided and this application Feb. 24, 1960, Ser. No. 10,769

3 Claims. (Cl. 250-211) The present invention relates to photocells andnovel methods of making same. This application is a division of mycopending application Serial No. 750,496, filed July 23, 1958, nowPatent No. 2,960,417.

The principal object of the invention is the provision of multiplephotocells of relatively small size suitable for use in automation, datareduction, process control, and the like where operation or control bymeans of a number of closely spaced photocells may be desirable. Anotherobject of the invention is to provide a compact photocell unit made upof a substantial number of closely spaced photocells. A further objectincludes the provision of a unique and relatively easy method ofpreparing multiple photocells of the type referred to above. Anotherobject of the invention is the provision of novel means for connectingto the cells. Other objects will also be apparent from the followingdetailed description of the invention.

Broadly stated, the method of preparing multiple photocells according tothe present invention involves the steps of applying a relatively widestrip coating of photosensitive material along the length of a threaded,or otherwise transversely grooved, dielectric rod or the like; thenmasking a longitudinal strip of the coating somewhat narrower than thewide strip of photosensitive material and applying a metallic conductiveovercoating on the photosensitive coating while maintaining the maskedstrip; then removing the mask and masking the grooves of the rod,preferably by winding a round rubber core or the like about the rod,followed by Sandblasting 0r otherwise removing all of the metallicovercoa-ting and photosensitive coating on the rod except for thatmasked in the grooves and then removing the mask from the grooves.

The present method, as briefly described above, gives a highly usefulphotocell unit comprising a plurality of small photocells positioned inthe bottom of the grooves of the rod. It will be appreciated that themethod makes it possible to provide a photocell unit having a largenumber of photocells over a small unit of length, the relative distancebetween the cells being dependent upon the spacing of the threads orgrooves in the rod. Typically, it is possible to provide as many as 32photocells, or even 67-70 cells or more, per inch of rod length by meansof the instant invention.

The invention will be more fully understood by reference to thefollowing detailed description thereof in connection with theaccompanying drawings wherein:

FIGURES l to 14 illustrate the various steps of the process and morespecifically:

FIG-URE 1 shows the rod coated with photosensitive material;

FIGURE 2 is a section taken along lines 2 2 of FIG- URE 1;

FIGURE 3 shows thc masking of a narrow strip of photosensitive material;

FIGURE 4 is a section taken along lines 4 4 of FIG- URE 3;

FIGURE 5 shows the metal overcoated rod;

FIGURE 6 is a section taken along lines 6 6 of FIG- URE 5;

FIGURE 7 illustrates the removal of the mask and the metallic coatingabove it;

3,037,122 Patented May 29, 1962 FIGURE 8 is a section taken along lines8 8 of FIGURE 7;

FIGURE 9 illustrates the masking of the grooves of the rod;

FIGURE l0 is a section taken along lines 10 10` of FIGURE 9;

FIGURE 1l shows the removal of the coatings on the raised positions ofthe rod;

FIGURE l2 is a section taken along lines 12 12 of FIGURE 1l;

FIGURE 13 shows the finished photocell;

FIGURE 14 is a section taken along lines 14 14 of FIGURE 13;

FIGURE l5 is a front view looking toward the photocell and showingelectrical contact with the photocell;

FIGURE 16 is a plan view corresponding to FIGURE l5 and;

FIGURE 17 is a section along lines 17 17 of FIG- URE 16.

Referring more specifically to the drawings, a threaded, or otherwiseannularly grooved, rod 2 of Suitable dielectric material, e.g., aceramic such as porcelain, is coated on one side, in the manner shown inFIGURES l and 2, with a relatively wide Strip of cadmium selenide,cadmium sulfide or other photosensitive material 4. The material may beapplied to rod 2 in any conventional fashion, eg., by aqueousSuspension, evaporation, silk screen, etc. The coated rod is thensuitably treated, eg., hea-ted at sufficiently high temperature tosinter the photosensitive material. The material may be sensitized atthis point also by any of several known methods, e.g., with halogens andcopper salts. A relatively narrower strip of the photosensitive coatingis then masked over the entire length of the coating. This may be donein a variety of ways, as for example by applying a removable tape ormasking strip 5 as shown in FIGURES 3 and 4 along the length of thecoating. masking is accomplished by placing the rod in a jig in such away as to cover a longitudinal strip of the photosensitive coating. Inany case, after the Strip of coating 4 is masked, a layer 6 ofconductive metal such as gold, silver, indium, etc., is applied over allof the coating 4, as shown in FIGURES 5 and 6 except for that covered bythe mask. This coating of metal, preferably gold, may be applied in anyconvenient manner, eg., by painting, dipping, spraying or the like.Preferably, however, the metal is applied by evaporation in a highvacuum. This insures a uniform conductive metal overcoating on all ofthe photosensitive surface except that covered by the jig or otherwisemasked. The gold or other metal overcoa-ting may be applied only on thatportion of -the rod that has been coated with the material 4. As analternative, the overcoating may be extended beyond the photosensitivematerial 4 to facilitate connecting the cells, as described hereinafter.

Following the application of the metal overcoating, the strip mask 5 isremoved together with the portion of the conductive metal coating abovethe strip 5, leaving the longitudinal strip of photosensitive material 4shown in FIGURE 2. As will be appreciated, the application of metalcoating 6 in the manner described above effectively forms a photocellextending the full length of the rod with a relatively short distance,i.e. the width of the masked strip, separating the electrodes.

The bottom portion of the grooves of rod 2 are then masked, preferablyby winding a round rubber cord 8 or the like under constant tension,into the threads or grooves in the manner shown in FIGURES 9 and 10. Thesize of the rubber cord or other masking means 8 should be chosen to fitwithin the grooves and effectively mask the metallic overcoating 6 andphotosensitive layer 4 in the bottom part of the grooves. The amount ofIn a preferred method, the' masking can be regulated by the tension ofthe rubber during the winding operations. Typically suitable windingtensions may be, for example, 4 to 6 oz. for rubber cord 1/32 indiameter.

The thus-masked rod is then sandblasted, or otherwise treated as shownin FIGURES 11 and l2, to remove all of the photosensitive material andconductive metal overcoating not masked by masking means 8 and lying onthe raised portion of the treated rod 2. The masking means '8 are thenremoved from the rod to leave a series of individual photocells, i.e.one photocell in the bottom of each group, along the full length of thethreaded rod. Each of these photocells as shown in FIGURES 13 and 14comprises spaced electrode portions formed by the metallic overcoating 6with the exposed photosensitive layer 4 therebetween.

If desired, all of the cells may be provided With a common connectionalong one side of the assembly. This may be accomplished by, forexample, the application of Silver paint or other suitable conductingmeans connecting all of the cells along one side.

FIGURES 15 to 17 also show a preferred arrangement for making contactwith individual cells. The arrange ment, as illustrated, includes a wirecomb made up of a series of highly conductive spring Wires 10, typicallyberyllium/copper Wire having a silver overcoat, embedded in a block 12of suitable non-conducting plastic such as polymethylmethacrylate or thelike. Each of the wires 10 is adapted to rest in the bottom of a groovefor contact with one of the electrodes 6 of the photocell. Such -contactis preferably completed by means of additional conductive metal, e.g.,silver paint, representing an extension 14 for each electrode. Thisextension may be provided for during the overcoating operation, asindicated heretofore, or by the application of silver paint or the likeafter the overcoating. Subsequent Sandblasting removes all of suchadditional metal except for the masked extensions in the bottom of thegrooves. As a further alternative, the extension may be formed by suit-,ably painting the grooves With silver or the like after theSandblasting operation.

As shown, the opposite free ends of the wires are so formed as to permitmaking connections with auxiliary equipment. It will be recognized thatthis arrangement makes it possible to have individual contacts forpractically any number of photocells, regardless of how closely spacedthe cells may be, since the free ends of wires 10 can be bent ordeformed as desired to make Whatever auxiliary connections arenecessary.

It is particularly desirable in practicing the method described hereinto subject the rod coated with photosensitive material to ionicbombardment prior to application of the overcoating metal. Typically,such bombardment may be carried out for a period of about 30 seconds to2 minutes using a pressure of the order of 1 mm. of mercury. Otherconditions normally employed in carrying out ionic bombardment may alsobe used. Such bombardment allows considerable control and modificationof the final electrical characteristics of the photocells describedherein. For instance, it has been found that ionic bombardment reducesthe light-on resista-nce of the photocells by a factor of 10 over theuntreated cells and does not seriously aifect the dark resistance.

It will be appreciated that the photocells described herein have avariety of uses. Typically, the present photocell units are useful inthe textile industry `for the purpose of regulating or controlling thefeed of fabric undergoing treatment. It will also be understood thatvarious modiiications may be made in the invention described hereinwithout deviating from the scope thereof as set forth in the followingclaims, wherein I claim:

l. A multiple photocell unit comprising a ceramic rod having a pluralityof transverse grooves extending the length thereof and an individualphotocell in the bottom of eac'n of said grooves, each photocell beingelectrically insulated from adjoining photocells and comprising a layerof photosensitive material and a pair of closely and transversely spacedopposed conductive metal layers overlying at least a portion of thephotosensitive material layer.

2. A multiple photocell unit according to claim 1 wherein said groovedrod is a threaded rod.

3. A multiple photocell unit according to claim l including means `forcontacting said cells, said means comprising a non-conductive blockhaving a plurality of conductive metal Wires connected thereto and eachof said wires contacting one of said photocells.

References Cited in the tile of this patent UNITED STATES PATENTS235,497 Ben et a1. Dec. 14, l1880 1,156,524 COX Oct. 12, 1915 1,767,715Stoekle June 24, 1930 2,243,132 Soller May 27, 1941 2,432,303 Fox Dec.9, 1947 2,839,646 Hester s June 17, 1958 FOREIGN PATENTS 216,492 GreatBritain June 4, 1924

